Optical waveguide modulator using single crystals of TlGaSe2 ORβTl2

Abstract

An optical waveguide modulator is disclosed which uses single crystals of TlGaSe 2 or TlInS 2 . The optical waveguide modulator is used to impress a signal upon a light beam traveling in a waveguide. Monochromatic light is guided along a thin plate of the crystal. Acoustic waves are generated which move across the thickness of the crystal, modulating the light. The frequency, polarization, or mode of the light can be modulated by the acoustic waves.

What we claim is: 
     
       1. An optical waveguide modulator comprising 1. a single crystal selected from the group consisting of TlGaSe 2  and β-TlInS 2  which is 1 to about 50 microns thick and at least about 3mm in width and length;   2. means for generating an acoustic wave in said crystal moving across the thickness of said crystal; and   3. means for passing a monochromatic light beam from an incoming waveguide through said crystal along the length of said crystal, then back into an outgoing waveguide.   
     
     
       2. An optical waveguide modulator according to claim 1 wherein said crystal is TlGaSe 2 . 
     
     
       3. An optical waveguide modulator according to claim 1 wherein said crystal is β-TlInS 2 . 
     
     
       4. An optical waveguide modulator according to claim 1 wherein said means for generating an acoustic wave is a transducer mounted on said crystal. 
     
     
       5. An optical waveguide modulator according to claim 4 wherein said transducer is a shear wave generating transducer which is mounted on said crystal so that the shear waves generated by it are perpendicular to the path of said light beam in said crystal. 
     
     
       6. An optical waveguide modulator according to claim 1 wherein said incoming waveguide is an optical fiber having a flat end which is cemented to one end of said crystal, and said outgoing waveguide is an optical fiber having a flat end which is cemented to the opposite end of said crystal. 
     
     
       7. An optical waveguide modulator according to claim 1 wherein said crystal is mounted on a flat substrate which has a lower refractive index than said crystal. 
     
     
       8. A method of modulating light comprising 1. passing a monochromatic light beam from an incoming waveguide through the length of a crystal selected from the group consisting of TlGaSe 2  and β-TlInS 2  which is 1 to about 50 microns thick and at least about 3mm in width and length, then coupling, said light beam to an outgoing waveguide; and   2. generating an acoustic wave in said crystal moving across the thickness of said crystal.   
     
     
       9. A method according to claim 8 wherein said crystal is TlGaSe 2 . 
     
     
       10. A method according to claim 8 wherein said crystal β-TlInS 2 . 
     
     
       11. A method according to claim 8 wherein said acoustic wave is generated by means of a transducer mounted on said crystal. 
     
     
       12. A method according to claim 11 wherein said acoustic wave is a shear wave propagated perpendicular to the path of said light beam in said crystal. 
     
     
       13. A method according to claim 8 wherein said incoming waveguide is an optical fiber having a flat end which is cemented to one end of said crystal, and said outgoing waveguide is an optical fiber having a flat end which is cemented to the opposite end of said crystal. 
     
     
       14. A method according to claim 8 wherein said light is coherent and has 1 to about 6 modes.